PTAB

IPR2024-00704

Vicor Corp v. Delta Electronics Inc

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1. Case Identification

2. Patent Overview

  • Title: Resonant Conversion System with Over-Current Protection Processes
  • Brief Description: The ’580 patent discloses a power conversion system comprising a buck converter that provides an input voltage to a downstream resonant converter. The system's purported invention is an over-current protection process that controls the buck converter to decrease the input voltage it supplies to the resonant converter when an over-current condition is detected.

3. Grounds for Unpatentability

Ground 1: Claims 1-3, 9-11, 13, and 17-18 are obvious over the PRM Datasheet in view of Hwang.

  • Prior Art Relied Upon: PRM Datasheet (a 2006 Vicor product datasheet), Hwang (Patent 6,674,272), and optionally the White Paper (a 2007 Vicor technical paper) or an Electronic Design article (a 2004 trade magazine article).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the PRM Datasheet disclosed the core architecture of the ’580 patent: a Pre-Regulator Module (PRM), which is a buck-boost converter, providing a regulated output voltage to a Voltage Transformation Module (VTM), which public documents like the White Paper explained was a resonant converter. The PRM Datasheet also disclosed that the PRM includes a pre-set, maximum current limit feature. However, it did not detail the implementation of this feature. Petitioner asserted that Hwang supplied this missing detail, teaching a current limiting technique for buck and boost converters where an excessive output current is detected, and the circuit is controlled to reduce its switching duty cycle, thereby decreasing the output voltage.
    • Motivation to Combine: Petitioner contended a person of ordinary skill in the art (POSITA), seeking to implement the circuit shown in the PRM Datasheet, would have been motivated to consult a reference like Hwang to implement the PRM's stated but unspecified current limit function. Hwang was directly relevant as it taught current limiting for the same type of switching converter (buck/boost) as the PRM. The combination involved applying a known technique to a known device to achieve a predictable result.
    • Expectation of Success: A POSITA would have had a reasonable expectation of success because modifying the switching duty cycle to impose a current limit was a well-understood technique for buck-boost regulators. The combination represented a simple incorporation of a known approach to provide a stated feature.

Ground 2: Claims 1-3, 9-11, 13, and 17-18 are obvious over the White Paper in view of Hwang.

  • Prior Art Relied Upon: White Paper (a 2007 Vicor technical paper) and Hwang (Patent 6,674,272).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground presented an alternative, obvious design choice. The White Paper, like the PRM Datasheet, disclosed the fundamental PRM-VTM (buck converter-resonant converter) architecture. Petitioner argued that instead of using the PRM's own internal current limit (as in Ground 1), it would have been obvious for a POSITA to implement an over-current protection scheme based on the current-handling capability of the downstream VTM. In this scenario, a current sensor would detect the VTM's output current (or a proportional signal), and the controller in the PRM would use Hwang's duty-cycle reduction method to limit current when the VTM's specific threshold was exceeded.
    • Motivation to Combine: Petitioner asserted that a POSITA would have been motivated to protect the entire system, not just the PRM. If the VTM had a lower current-handling capability than the PRM, a common and predictable design choice would be to set the system's over-current protection threshold to protect the more vulnerable component (the VTM). This ground argued it was an obvious choice to use the VTM's current limit as the trigger for the PRM's protective action, using the well-known mechanism taught by Hwang.
    • Expectation of Success: A POSITA would have expected success because the combination involved a routine modification of a feedback control loop to protect a downstream component, which was well within the ordinary skill in the art of power electronics design.

4. Key Claim Construction Positions

  • "when the resonant converter generates the over-current": Petitioner's arguments for both grounds relied on the Patent Owner's "Apparent Construction" from the co-pending litigation. In that litigation, the Patent Owner allegedly contended this limitation is met when a current limit is reached in the upstream PRM (buck converter) because the VTM's (resonant converter's) output is proportionally related to its input from the PRM. Petitioner argued that under this construction—where an over-current condition in the PRM "equates to" an over-current condition in the VTM—the claims were rendered obvious by prior art that disclosed a PRM with its own current limit feature.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued against discretionary denial under both 35 U.S.C. §325(d) and §314(a).
  • §325(d): Petitioner asserted that the prior art references and grounds in the petition were new and non-cumulative to the art considered by the examiner during prosecution, thus denial under Advanced Bionics would be inappropriate.
  • §314(a) (Fintiv): Petitioner contended that the Fintiv factors favored institution. It argued the parallel district court litigation was in its earliest stages with no trial date set and minimal investment. Petitioner stated its intent to seek a stay and stipulated that, if the inter partes review (IPR) is instituted, it would not pursue the same invalidity grounds in the district court, thus minimizing overlap.

6. Relief Requested

  • Petitioner requested institution of an IPR and cancellation of claims 1-3, 9-11, 13, and 17-18 of the ’580 patent as unpatentable.